The walkers were also more likely to smoke but more likely to eat fruit, the study found.
After the six-year follow-up, both groups lost weight. But the male runners and the heavier female runners had better results.
"An overweight woman of average height and a BMI over 28 might expect to lose 19 pounds by adding a 3.2-mile run to her daily routine, but only 9 pounds by expending the same amount of energy by walking," Williams said. That total weight loss occurs gradually, but effects are seen from the start.
Running also takes less time to produce the same amount of effort, Williams said. For instance, that same woman would need to walk 4.6 miles at a brisk pace to expend the effort of running 3.2 miles. The run would take about 40 minutes; the walk about an hour and 20 minutes, he said.
One reason that running produces more weight loss is metabolic. "If you exercise vigorously like running, your metabolic rate remains elevated after the exercise," Williams said. "For walkers, much less so."
It's also been shown that vigorous exercisers who overeat are good at compensating later, he said. "If runners overeat one day, they make up for it the next," he said.
Williams decided to study running and walking because "runners and walkers think about how much they are doing by how far they go," he said. Gym rats, on the other hand, are less accurate about reporting their exercise time, he said.
The findings are no surprise, said Dr. Tim Church, director of preventive medicine research at Pennington Biomedical Research Center, Baton Rouge, who was not involved in the study.
But Church said running itself shouldn't get all the credit for the weight control. "People who are running are more focused on other weight issues," Church said. "I guarantee you, the runners are way more focused on their diet than the walkers."
And that's a
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